The decision to entrust American democracy to computers is likely to come under scrutiny in the wake of yesterday's elections as widespread reports of glitches in new electronic voting machines raised the spectre of legal challenges to the results.

"We're getting reports from all over the place. I can't get them up on our website fast enough," said Warren Stewart, the policy director of VoteTrustUSA, a watchdog organisation. "Machines of all different makes are breaking down."

In Indiana, all the voting machines in Delaware County failed to function when election workers tried to start them up yesterday morning, and early voters were turned away. The county extended its voting hours to compensate.

In Ohio, 40 polling stations in Cuyahoga County reported problems with their machines. In some places, poll workers were resorting to paper ballots.

In Florida, the Palm Beach Post reported complaints from some voters that the machines had recorded their votes wrongly. They would press the screen by one candidate's name, and a tick appeared by another's. There were calls yesterday for the machines to be impounded.

At one polling site in Maryland, officials accidentally turned the machines off by using the wrong key card. In Utah, there were problems with machines used to encode swipe cards for individual voters, delaying the start of voting. Elsewhere, the machines' touch screens cut short the full name of the candidate if it was over a limited number of letters.

Electronic voting was supposed to fix the problems in America's electoral system revealed in the 2000 presidential election, which ended up literally hanging by chads, the detritus from punchcard ballots. Those ballots are a thing of the past, except for a few counties in Idaho.

The 2002 Help America Vote Act pumped $3bn (£1.6bn) into new technology, with the result that nearly 40% of registered voters were expected to cast their ballots electronically this year, mostly in the east of the country.

There is some doubt, however, over whether the cure has been worse than the disease. "It depends. In some places it's better. In some places it's worse," said Curtis Gans, the head of the Centre for the Study of the American Electorate. "We had better be better prepared in 2008."

When the machines break down, voters can use provisional paper ballots, but there is scepticism over whether they will be counted. In 2004, 676,000 provisional ballots were never counted because of mistakes and discrepancies.

The biggest political problem behind the use of electronic machines is that they are made by private companies who retain proprietary control over their software, and who have affiliations of their own. In 2003, it turned out that the chief executive of one of the companies, Diebold, pledged his support to the president.